Ethylbenzene disproportionation



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United States Patent This invent-ion relates to the''disproportionaition or ethylbenzene to a mixture offdiethylbenzene andtriethylbenzene wherein the- 'triethylbenzene predominates.

Earlier work on the (lisproportionation of ethylbenzene in the presence of HRBFa "treati'n'gi agent-has indicated that diethylbenzene is the predominant disproportionation product and under certainconditionsthe only polyethylbenzene produced (U. S. -2,528;89-3).

Ithas *further been thought necessary in theprevious work that-triethylbenzene in-lar-ge yield -could-be ob tained only by disproportionating'diethylbenzene in -the presence of HF-BF treating agent S. 2, 6 44;01r7.-) At'the present-time, a-mar-ket has developed for both diethylbenzene and triethylbenzene, preferably the 13* d-iethylbenzene and the 1,3;-triethylb'enzene: Economic -considerationsmake inmost-desirable that. both of these polyethylbenzenes be obtainable in high yield directytrom the monoethylbenzener" I An object of the inventionisa process-fortheproduction of L,3-diethy1benzeneand i -1:,3,S tPiethylbenZenei n' high yieldby the disproportionation of. monoethylbeh-a zene.

A particular object 1 of the invention 'is a process forv the *disproportionation of ethylbenzene to a reactioii product containing. diethylbenzene and triethylbenzene wherein the triethyl-benzene yield predominates =ov'e1- the diethylbenzene yield.

A reaction product mixture containing =l ,'3-diethylbenzene and -l,3,-5-triethylbenzene wherein the triethylben zene' predominates over the. diethylbenzene is "obtained when ethylbenzene is contacted under substantially anhydrous conditions in the absence of 'reacti ve hydrm carbons with HF-BF3 treating. agent aha-temperature 0t at least about 75 C. fora sufiicienttime. The=liquid HE is present inan amount: of at least about 3 -'moles," preferably between -about.6 and about l-Zrmdles pe'r mole: of ethylbenzene. At least about 0:4 molepreferably about -1 mole, of BF3 ispresentpermole'of ethylbehzene: An essentially. constantyieldof diethyl-ben'zene and' tri ethylbenzene-J's obtainedat a-te'mperaturebetweeniabout 80 'C. and about 140 C.-whenl the reaction iszcarried out for artiine between about one-halfhour and about 3 minutes, the longer times cortespbndihgidthe lower temperatures.

In order to obtain a reactionproduct *mixturewherein the triethylbenzene component predominates over. the diethylbenzenecomponent, it is necessary-"to control both. the temperatureandthe time of "contacting. Afreasom ablyfshort time of contactingiproduces a:reaction product mixture wherein the triethylbenzene*componentpreclomi natesover the diethylbenzene component when. the con-s tacting is carried out -'at-a temperature of about 7510. As the'te nperature of contacting is increased,--the time" of contacting needed to produce. the .predominaritly=;tri' ethylbenzene disproportionation product decreases; Temperatures as-high-as, 175 *C; or even-higher may be utilized; however, ;the operation at these }high tempe'ratufes results in side reactions suc h as craclging and "ice tar' -forniation even when: the timeof fcontacting; is very short;

The ethylbenzene 'disproportioha'tion reaction appears,

to :reach theconstant reaction product distribution when sufficient tii'ne is'given at the particular temperature.

The essentieillyw'onstara'tproduct distribution contains about 15 mole percentof l,-3-diethylbenzene andabout 23 mole percentof-=1;3 ,5-triethylbenzenea It is .-p"referr e"cl to -oper ate at a-temp'e'rature between about C. and

about- 'C. At-these temperatures, vthe substantially. constant reactidntp'roduc't distribution is obtained at times of contacting between about one-half hour and about 3 minutes, the longer-times corresponding; to the lower:

. the 'I-I'F-Bl-aiagent and do not participate in any "reaction.

with the ethylbenzene 'charged. Examples of reactive hydrocarbons are -olefins, .toluene; xylene, ethyltoluene; and isopropyltoluene. Examples of non-reactive hydrocarbons are: isopentane, butane and hexane. It -is;pre-' fer-redthat benzene. be. absentfrom the feedas its presence has an adverse effect on the degree of dis proportionation.

The process: utilizes substantially: anhydrousfiliquid hydrogen fluoride. The liquid -hydrogen -fluoride should not eontainmore than-about2 or 3% of water. Corn mercial grade anhydrous hydrofluoric acid is suitable for this process. 7

Under the conditions lot the process,polyeth-ylbenzenes form a'complex-containing 1-mole of BF and, .it'is believed, 1--mole"of HF; Therefore, at least enough liquid HF must be present to participate in the-formation of the complex with tbe polyethylbe'nzene;inaddition to this vamount, sufiicient liquid HF'must be present to dissolve the complex which has been formed; In general, the presence -of a distinct separate acid phase: in the contacting zone indicates that -at least the minimum requirement of liquid has been met. More than-this minimum amount of liquid HF is desirable. Usually between about Sand '50 molesof liquid HF are utilized ,per mole of ethylbenzene eharged 'to the process. It is preferred to'operate with between about'- andl 2 moles of liquidI-IF per mole of ethylbenzene charged.

The process requires thepresence of -.at least an amount; ofboron-trifluoride' sufiicient to cause-thedisproportionation:reaction to=take place. While amounts of B1 aswsmall as 0.1 mole per a mole of ethylbenzene charged. will 'cause an appreciable arnount-ofdispropor tionation to take place, it is desirable -to-operate :withrat least about 0.4 mole of BB. More BFs has a beneficial efiect on the degree of the disproportionation reactions It is preferred to use about l mole per m'ole of ethylbenzene in the feedieven though'asmuch as :3 or more moles-inay -be-used. 1

The process mayfbe operatedwith two liquid phases present in the contacting-lone. At 2 high BF usages; a. gas phase may also be present in-the contacting rzone; The two liquid phaseswillbe spoken .of herein as the rafiinate phase'and 'the acid phase. The acid phase consists of liquidI-IR BFa complex and physically dis solved hydrocarbons. The rafiinatephasemay be' ethyl-s benzene inexcess of that-amount takenintothe'acid phase, or may be a mixture of ethylbenzene and tinert hydrocarbons, or. may be -principally:inertlhydrocarbons. In a the Y absence of substantial amounts 'ofgine'rt hydro! carbons -the an ounfiof raifinate phase; isdependent=upon Patented Dec. 4.1 956 3 the amount of BF3 utilized. When using at least about 0.4 mole of BF3 per mole of ethylbenzene, and in the substantial absence of inert hydrocarbons, all or virtually all the unreacted ethylbenzene will be taken into the acid sufficient BF; is present to complex all of the polyethylbenzene formable. A substantial amount of the ethylbenzene will remain in the raffinatephase, even when using somewhat more than 0.4 mole of BF:; per mole of ethylbenzene groups charged. All the ethylbenzene in the raffinate phase does not undergo a rearrangement reaction, even under conditions of good agitation. (The presence of dissolved inert hydrocarbons in the acid phase does not appear to have any adverse effect on the degree or direction of the rearrangement reactions.)

In order to maximize the yield of conversion products, it is preferred to operate under conditions which form a single essentially homogeneous liquid phase in the contacting zone. A single essentially homogeneous liquid phase is attainable with a feed containing as much as three volume percent of parafiinic hydrocarbons. Large amounts of benzene may be dissolved in the acid phase, as much as 1 mole or more, per mole of complexed polyethylbenzene, depending on the amount of complex in the acid phase. (It is to be understood that a separate gaseous BFs phase may also be present, but it is preferred that a minimum of free space be present in the contacting zone and that sufficient pressure he maintained to insure that essentially all the BF3 is either in the complexed form or is in physical solution in the acid phase.)

The reaction product mixture may be recovered from the acid phase by various methods. Probably the simplest procedure and one most suitable for laboratory work consists of adding the acid phase to crushed ice; or the acid phase may be contacted wtih cold aqueous alkaline solution, such as sodium hydroxide, potassium hydroxide and ammonia. It is desirable to prevent rearrangement reactions by the use of a cold aqueous reagent.

The hydrocarbons originally present in the acid phase appear as an upper oil layer above a lower aqueous layer. The upper oil layer may be separated by decantation and may be treated with dilute aqueous alkaline solution to remove any remaining HF and ER; occluded therein.

Both HF and BFs are relatively expensive chemicals and it is desirable in an economic process to recover these and to recycle them for reuse in the process. The HF and BF; may be readily removed from the: acid phase by heating the acid phase or by applying a vacuum thereto. The HF and the BF: distill overhead and may be recovered for reuse in the process.

EXAMPLES The results obtainable by the invention are illustrated by several examples set out below. The runs were carried out using a carbon steel reactor provided with a 1725 R. P. M.- stirrer. The order of addition of materials to the reactor was: (1) ethylbenzene of CP quality, (2) commercial grade anhydrous liquid HF and (3) commercial grade BFa. The contents of the reactor were agitated during the addition of the HF and BFa; the agitation was continued while the reactor was brought to the desired contacting temperature and was maintained during the contacting time. The contents of the reactor were withdrawn into a vessel filled with crushed ice. An upper aqueous hydrocarbon layer formed above a lower aqueous layer. The hydrocarbon layer was decanted and washed with dilute ammonium hydroxide solution to remove HF I and BFa. The neutral hydrocarbons were water washed Table 1 Run No I II III IV Temperature, "C. Time, Minutes Ethylbenzene, moles..- 2. 86 2. 54 2. 84 3. 71 HF, moles 35 35 28 35 BF moles 3. 50 2. 94 3. 75 3. 75 HF/Ethvlbenzcne. 12.2 13. 8 9. 8 9. 4 BF /Ethylbenmne 1. 22 1. 16 1. 32 1. 00 Reaction Product, mole perce enzene 49 5G 60 Ethvlbenzene 4 4 2 1. 3-diethvlbenzene..- 1.3 S-triethvlbenzene. Percent disproportionatiom..-

Franction to di- Fraction to tri- 31 77 70 Within the limits of experimental error, the physical properties and the infrared spectra show the diethylbenzene product fraction to be the single isomer 1,3-diethylbenzene; and the triethylbenzene fraction to be the single isomer 1,3,5-triethylbenzene. In none of these tests was there found any polyethylbenzene having more than 3 ethyl groups. A

Under the conditions of these experiments, essentially the only difference between the runs was the temperature of contacting. In run I, which was carried out at 50 C., only 31% of the ethylbenzene which disproportionated was converted to the triethylbenzene; the molar ratio of triethylbenzene to diethylbenzene in the reaction product mixture was about 1:4. At the 80 C. temperature of run II, the polyethylbenzene product distribution changed completely. In run II, 70% of the ethylbenzene which disproportionated went to produce triethylbenzene, i. e., just about the reverse of the results of run I. Runs III and IV which were carried out at C. and C. respectively, show that the reaction product attains a substantially constant distribution with about 97% of the ethylbenzene charged disproportionated. It appears that the substantially constant product distribution contains a mole ratio of triethylbenzene to diethylbenzene of about 23:15, which represents about 70% disproportionation of the ethylbenzene to 1,3,5-triethylbenzene.

It is seen that by proper control of operating conditions, particularly temperature and time, it is possible to convert ethylbenzene directly to a reaction product mixture containing both diethylbenzene and triethylbenzene and wherein the triethylbenzene component predominates over the diethylbenzene component. Furthermore, it'is possible to attain a reaction product mixture having an essentially constant distribution of polyethylbenzenes which may or may not be an equilibrium condition.

Thus, having described the invention, what is claimed is:

1. A disproportionation process which comprises contacting ethylbenzene, in the absence of reactive hydrocarbons, under substantially anhydrous conditions, with at least about moles of liquid HF and with at least' about 0.4 moles of BF3 respectively per mole of ethyl benzene at atemperature of at least 75 C. for about a time at least one-half hour, thereby producing a reaction product mixture wherein triethylbenzene predominates over diethylbenzene and removing HF and BFs to obtain a reaction product mixture comprising essentially benzene, ethylbenzene, 1,3-diethylbenzene and 1,3,5-triethylbenzene. 1 I

2. The process of claim 1 wherein said liquid HF is present in an amount between about 6 and about 12 moles per mole of'ethylbenzene.

3. The process of claim 1 wherein said BF3 is present in an amount of about 1 mole per mole of ethylbenzene.

4. A disproportionation process which comprises contacting, under substantially anhydrous conditions, a feed comprising essentially ethylbenzene with between about 3 and 50 moles :of liquid HF per mole of ethylbenzene in said feed and'with between about 0.4 and 3 moles of BF3 per mole of ethylbenzene in said feed at a temperature between about 80 C. and about 140 C. for a time between about one-half hour and about 3 minutes, the longer times corresponding to the lower temperatures, and removing HF and BF to recover a reaction product mixture comprising essentially benzene, ethylbenzene, 1,3-diethylbenzene, and 1,3,5-triethylbenzene wherein the mole ratio of said triethylbenzene to said diethylbenzene is about 23:15.

References Cited in the file of this patent UNITED STATES PATENTS 2,528,893 Lien et al. Nov. 7, 1950 2,564,073 Lien et a1 Aug. 14, 1951 2,644,017 McCaulay et al June 30, 1953 2,683,759 McCaulay et al. July 13, 1954 

1. A DISPROPORTIONATION PROCESS WHICH COMPRISES CONSTACTING ETHYLBENZENE, IN THE ABSENCE OF REACTIVE HYDROCARBONS, UNDER SUBSTANTIALLY ANHYDROUS CONDITIONS, WITH AT LEAST ABOUT 3 MOLES OF LIQUID HF AND WITH AT LEAST ABOUT 0.4 MOLES OF BF3 RESPECTIVELY PER MOLE OF ETHYLBENZENE AT A TEMPERATURE OF AT LEAST 75* C. FOR ABOUT A TIME AT LEAST ONE-HALF HOUR, THEREBY PRODUCING A REACTION PRODUCT MIXTURE WHEREIN TRIETHYLBENZENE PREDOMINATES OVER DIETHYLBENZENE AND REMOVING HF AND BF3 TO OBTAIN A REACTION PRODUCT MIXTURE COMPRISING ESSENTIALLY BENZENE, ETHYLBENZENE, 1,3-DIETHYLBENZENE AND 1,3,5-TRIETHYLBENZENE. 